dct1 = {}
dct2 = {'a':1,'b':'hello'}
print(dct1,dct2)
dct2['a'] = 3
print(dct2)
dct2['c'] = None
print(dct2)
#绿色的方法重点常见
dct1.update(dct2)
print(dct1)
print('c' in dct1)
dct1.get('a')
print(dct1.get('a'))
dct1.keys()
print(dct1.keys())
for x in dct1.keys():
    print(x)
print(dct1.values())
for x in dct1.values():
    print(x)
print(dct1.items())
for key,values in dct1.items():
    print(key,'=====',values)